In recent years, an imaging sensor, such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal-Oxide Semiconductor), and a signal processing circuit are increasingly improved in terms of integration density and come to be available inexpensively. Accordingly, a digital still camera and a digital video camera (hereinafter simply referred to as a “digital camera”), which are capable of converting an optical image of an object into an electrical image signal and outputting the same, are rapidly growing popular.
FIGS. 14A to 14C are diagrams each showing a relation between an attitude of the digital camera and an attitude of a picked up image displayed on a display section thereof. As shown in each of FIGS. 14A to 14C, a photographer performs shooting by changing the attitude of a digital camera 100 in accordance with a shooting intention. For example, in the case of shooting a horizontally oriented object such as a landscape, the photographer turns the attitude of the digital camera 100 so as to be in a horizontally oriented state and then performs shooting. On the other hand, in the case of shooting a vertically oriented object such as a person and a building, the photographer turns the attitude of the digital camera 100 so as to be in a vertically oriented state and then performs shooting. Hereinafter, as shown in FIG. 14A, the attitude of the digital camera 100 when a stroke direction of a shutter button thereof is in parallel with the gravity direction is referred to as a horizontal shooting attitude. On the other hand, as shown in FIG. 14B, the attitude of the digital camera 100 when the stroke direction of the shutter button is perpendicular to the gravity direction is referred to as a vertical shooting attitude. Further, images shot in the respective attitudes are referred to as a horizontally shot image and a vertically shot image, respectively. In the conventional digital camera 100, a shot image is displayed in the same direction as the attitude of the digital camera 100 at the time of shooting. That is, in the case where an image shot in the vertical shooting attitude, as shown in FIG. 14B, is displayed on the display section while the digital camera 100 is situated in the horizontal attitude, as shown in FIG. 14C, an orientation of the shot image displayed thereon is different from an orientation of the image at the time of the shooting. Therefore, in the case of displaying a series of shot images in which vertically shot image and horizontally shot image are mixed together, a problem of difficulty in viewing is caused since the orientation of the vertically shot image is different from the orientation at the time of the shooting.
Against this problem, Japanese Laid-Open Patent Publication No. 2001-45354 (hereinafter referred to as Patent document 1) discloses a technique of providing an imaging device having rotation state detection means for detecting a rotation state of photoelectric conversion means and adding means for adding rotation state information at the time of the shooting to an image signal obtained based on an output from the photoelectric conversion means.
By adding the rotation state information to the obtained image signal, the attitude of the digital camera at the time of the shooting is detected, whereby a display in accordance with the attitude at the time of the shooting can be performed regardless of whether the image is shot in the horizontal shooting attitude or in the vertical shooting attitude.    Patent document 1: Japanese Laid-Open Patent Publication No. 2001-45354